"There are definitely Easter eggs throughout the upcoming episodes that might give you a glimpse of an alternative future that might come to pass," he hinted.

Kreisberg also refused to rule out an appearance from further DC characters, such as the rumored Batman.

"Aside from the characters that wouldn't fit into our conception of Oliver's world, like some of the more fantastical aliens or super-powered people, everybody is really sort of up for grabs," he explained.

Arrow premieres on Wednesday, October 10 at 8/7c on The CW. The series will air on Sky1 in the UK.